A battery assembly is disclosed that includes a battery housing, a battery array, and one or more cooling plates. The battery housing forms a battery compartment having a width and length greater than a height. The battery array includes a plurality of cylindrical battery cells oriented horizontally with an axis substantially perpendicular to the height of the battery compartment. The plurality of battery cells is organized into a plurality of rows within the battery compartment. The plurality of battery cells is stacked two or more battery cells deep within the plurality of rows. The one or more cooling plates are oriented perpendicular to the axis of the battery cells and positioned proximal to an end of battery cells within a row of the plurality of rows.